LONDON – In another dark day for the British retailing industry, Debenhams said Tuesday it will start liquidating its business after a potential buyer of the company pulled out, a move that looks like it will cost 12,000 workers their jobs.The 242-year-old department store chain said administrators had decided to start winding down operations while continuing to seek offers “for all or parts of the business.”JD Sports had been mulling an offer for Debenhams, which like others in the U.K.